A 16-year-old child with ARDS is being treated with mechanical ventilation and PEEP. The patient has persistent hypoxemia. This would result in an increase in which of the following hemodynamic measurements?

• A. PAP
• B. CVP
• C. PCWP
• D. Qt (cardiac output)

Answer: (A)

PEEP raises intrathoracic and alveolar pressures, which can increase resistance in the pulmonary vasculature, especially in diseased lungs like ARDS. This rise in pulmonary vascular resistance makes the right heart work harder to push blood through the lungs, raising the pressure in the pulmonary arteries. While venous return can be reduced (potentially lowering cardiac output) and left-heart filling pressures may stay the same or even fall, the most direct and characteristic change in this scenario is an elevation in pulmonary artery pressure.